Historically, those Hobbits who would take up the defence of their land under the direct commmand of the Shire-thain. We're told almost nothing about their organisation, but what hints we have seem to indicate that they were a militia (that is, a force of ordinary Hobbits who would come together to deal with emergencies as they arose) rather than any kind of standing army.

By the time of the War of the Ring, the Hobbitry-in-arms had not been mustered for centuries (indeed, the force had probably not existed in any practical terms since the Battle of Greenfields, nearly three hundred years earlier). Nonetheless, when Sharkey and his ruffians invaded the Shire during that War, the Hobbits were mobilised by the returning Travellers, and succeeded in reclaiming their land.